It has long been recognized that, in apparatus that treats a flowing gas stream and/or constituents entrained or incorporated therein, a uniform distribution of the incoming gas stream into operative relation with downstream treating elements will result in increased efficiency of operation and extended life of the involved operating components. One area of preferential concern has been in the field of industrial filtration devices, commonly called "baghouses" or dust collectors, which typically employ a large number of filter assemblies, normally tubes or panels, interposed in the path of a flowing gas stream to separate particulate matter suspended and being carried in such flowing gas stream.
In such dust collectors the particulate laden gas stream most commonly enters the filter housing through a breach in the lower housing wall defining a pyramidal or conical dust collecting hopper. Ideally, but not in practice, such particulate laden dust stream then dispenses to uniformly fill the housing and to uniformly pass through the filter media with the entrained particulates being separated by and remaining on the surface of the filter media. The accumulation or build up of separated particulates on the upstream surface of the filter media creates an increasing pressure drop across the filter media and which, unless removed by dislodgement of the particulates, will effect a reduction in the rate of gas flow through the unit. In order to avoid such particulate accumulation on the upstream surface of the filter media, the filter media is periodically cleaned by utilization of various techniques such as pulse jet, reverse flow and shaking. The outcome of such cleaning is that a large portion of the accumulated particulates drops off the filter media and falls downwardly into the collection hopper.
In many industrial filter housings the particulate bearing gas stream enters the filter housing through a breach in the dependent material collection hopper at a sufficiently high velocity, usually in the order of 3500 feet per minute, to maintain the entrainment of the particulates being conveyed directly. As will be apparent such incoming gas stream would not normally slow down and disperse to fill the housing but rather would remain concentrated in a high velocity flow stream that would effect non uniform deposition of the particulates on the filter media and high degrees of localized abrasion on the filter components due to the effects of high velocity impingement of often abrasive particulates thereon. In addition, the inherent traversing of the input gas stream by the dislodged particulates attendant the cleaning operation other results in an untoward degree of particle reentrainment and consequent drop in operating efficiency.
The problem of the destructive and operationally denigrating effects attendant the high speed introduction of the incoming gas stream into the filter housing has been long recognized. In order to alleviate such destructive and operationally denigrating effects the art has taught the interposition of baffles and/or diffusing devices in the path of the incoming gas stream. Initially such baffles were no more than the interposition of a solid plate in and disposed perpendicular to the path of the incoming air stream. Later designs included the interposition of baffle plates at varying angles to the incoming gas stream and the utilization of selectively shaped perforated diffuser elements in the path of the incoming gas stream. Exemplary of the latter approach is U.S. Pat. No. 3,831,354. While such perforated plate diffuser designs did operate to somewhat reduce or ameliorate the abrasive wear and uneven distribution of gas flow they did not solve the basic problem inherent therein.